(1) Field of the Invention
The present invention relates to a three-way ball valve used in a pipeline for various fluids, more specifically to a three-way ball valve of a vertical type having two independent flow passages within a ball and able to simplifying the piping.
(2) Description of the Related Art
Conventional vertical type three-way ball valves are mainly classified into a two-port type wherein two openings are provided in a ball arranged within a valve body and into a three-port type wherein three openings are provided in the ball. That is, in a ball valve structure shown in FIG. 7 wherein an inlet 11 is provided in the axial direction of a stem 8 fitted in a ball 18 and other inlets 9 and 10 are provided in the same plane as the former inlet at a right angle thereto on the opposite sides, the ball 18 of the two-port type accommodated within a main body 1 is shown in FIG. 8, having a port 20 oriented in the axial direction of the stem 8 and a port 19 oriented in a direction vertical to the axis of the port 20; and the ball 18 of the three-port type is shown in FIG. 9, having a port 21 and a port 22 corresponding to the ports 19 and 20 of the two-port type, respectively, and a further port 23 oriented in the direction vertical to the axis of the port 21.
However, in the two-port type, while a flow passage (FIG. 10a) communicating the inlet 10, the port 19, the port 20 and the inlet 11 with each other and a flow passage (FIG. 10b) communicating the inlet 9, the port 19, the port 20 and the inlet 11 with each other are formed by the rotation of the ball 18, it is impossible to form a flow passage communicating the inlet 9 with the inlet 10.
On the other hand, in the three-port type, it is possible to form not only a flow passage (FIG. 11a) communicating the inlet 10, the ports 21, 22 and the inlet 11 with each other and one (FIG. 11b) communicating the inlet 9, the ports 23, 22 and the inlet 11 with each other, but also a flow passage (FIG. 11c) wherein the ball 18 is located at a position of an intermediate opening degree so that both the former flow passages are communicated with each other. This, however, has a problem in that if one wishes to use a flow passage communicating the inlet 9 with the inlet 10 alone, the inlet 11 must be shut, which necessitates one more valve in a piping line on the inlet 11 side, resulting in a complication, of the piping.